The present invention relates to data storage systems, and more particularly, this invention relates to a method for dynamic consistency group formation in a storage system.
A possible and continuing goal in the data storage industry is that of data consistency, which has become a focal feature of modern data storage systems. The continuing benefit for increasing consistency has spawned an industry dedicated to providing storage solutions to enterprise customers with huge storage capacity and stringent data consistency requirements.
Data stored on a source storage system and a target storage system should be consistent with respect to both data content and data structure. As such, data are typically migrated to the target storage system in the same order as they were written to the source storage system. Since migration of data to the target storage system often occurs concurrent to writing the data to the source storage system or using the data on the source storage system, events occur where data being written is simultaneously being accessed and/or changed on another system, known as collisions. These collisions dictate that the migration to the target storage system wait for completion of the corresponding write operation to the source storage system, resulting in unacceptable latency during write and migrate operations.
In an increasingly global economy, where business often occurs internationally and storage needs span the globe, increased latency affects the performance and viability of storage systems, particularly when considering that the distance between the source storage system and the target storage system, which is quite common in the global economy, greatly amplifies the latency experienced during a given collision.
Current state-of-the-art techniques employ several approaches to provide users with an acceptable consistency within storage systems, including symmetrical (synchronous) solutions and asymmetrical (asynchronous) solutions.
Symmetrical storage solutions copy data written to a source storage system from the source storage system to a target storage system, and then copy the data back to the source storage system. This solution guarantees consistency among the source data and target data, but also results in collisions. Therefore, symmetrical storage solutions suffer from latency that detracts from data accessibility and inhibits or even prohibits deployment of the storage solutions in practice.
Asymmetrical storage solutions copy data from a source storage system to a target storage system, which may be recovered on demand. Asymmetrical storage solutions do not suffer from collisions as frequently as symmetrical solutions, since the data transmission is unidirectional, but neither can they guarantee consistency, especially with regard to data structure. Therefore, asymmetrical storage solutions are inadequate to meet current industry data consistency needs.
Therefore, a method for ensuring consistency of data between a source storage system and a target storage system that minimizes latency caused by collisions would find great utility and benefit in the data storage industry.